1. Field of the Invention
The present invention relates to a method for reprocessing solid polyester material and an apparatus for carrying out the method.
2. Description of Related Prior Art
Polyester material, such as polyethylene terephthalate or PET, substantially sorted and pure, results from recycling of material or as polyester educt. Methods which employ inert gas, vacuum and elevated temperature are known for processing polyester material in the solid phase. In such processes, the polyester is frequently subjected to specific conditions, as described in the German reference no. OS 31 05 767.
In a number of known methods for the recycling of polyethylene terephthalate (PET) production waste, the problem of melting mixed recycling material with glycol or dicarboxylic acid ester (esterification product) is solved, for instance, in the corresponding processing stage of the manufacturing process. In this procedure, as disclosed in British Patent 1 254 209, hydrolysis or glycolysis of the long-chain molecules and the mixing of thermally stressed and possibly damaged molecules with the reacting esterification product takes place. The material being treated must again pass through the esterification process and the polycondensation process with the thermal stressing inherent therein. Since all the substances that are present as a result of the equilibrium reaction, such as for instance aldehydes and ether compounds or cross-linked products, are introduced with the recycling material, side reactions cause defective places in the condensing polymer molecules.
Therefore, an object of the present invention is to provide a method, and an apparatus for carrying out the method, which makes it possible to work up a polyester material to a high-grade final product in a minimum processing time, with the smallest possible thermal stress, and with the admixing of the smallest possible amounts of the primary material.